User Contributed Notes 6 notes

I found this function useful when uploading a file through FTP. One of the files I was uploading was input from a textarea on the previous page, so really there was no "file" to upload, this solved the problem nicely:

No, the fseek() is necessary - after writing to the file, the file pointer (I'll use "file pointer" to refer to the current position in the file, the thing you change with fseek()) is at the end of the file, and reading at the end of the file gives you EOF right away, which manifests itself as an empty upload.

Where you might be getting confused is in some systems' requirement that one seek or flush between reading and writing the same file. fflush() satisfies that prerequisite, but it doesn't do anything about the file pointer, and in this case the file pointer needs moving.

Beware that PHP's tmpfile is not an equivalent of unix' tmpfile.PHP (at least v. 5.3.17/linux I'm using now) creates a file in /tmp with prefix "php", and deletes that file on fclose or script termination.So, if you want to be sure that you don't leave garbage even in case of a fatal error, or killed process, you shouldn't rely on this function.Use the classical method of deleting the file after creation:<?php$fn = tempnam ('/tmp', 'some-prefix-');if ($fn) {$f = fopen ($fn, 'w+');unlink ($fn); // even if fopen failed, because tempnam created the fileif ($f) {do_something_with_file_handle ($f); } }?>